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<div class="titlepage"><div><div><h4 class="title">
<a name="beast.ref.boost__beast__http__async_write_header"></a><a class="link" href="boost__beast__http__async_write_header.html" title="http::async_write_header">http::async_write_header</a>
</h4></div></div></div>
<p>
        <a class="indexterm" name="idp104702848"></a>
Write a header to a stream asynchronously using a
        serializer.
      </p>
<h5>
<a name="beast.ref.boost__beast__http__async_write_header.h0"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__http__async_write_header.synopsis"></a></span><a class="link" href="boost__beast__http__async_write_header.html#beast.ref.boost__beast__http__async_write_header.synopsis">Synopsis</a>
      </h5>
<p>
        Defined in header <code class="literal">&lt;<a href="../../../../../../boost/beast/http/write.hpp" target="_top">boost/beast/http/write.hpp</a>&gt;</code>
      </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">class</span> <a href="../../../../../../doc/html/boost_asio/reference/AsyncWriteStream.html" target="_top"><span class="bold"><strong>AsyncWriteStream</strong></span></a><span class="special">,</span>
    <span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span>
    <span class="keyword">class</span> <a class="link" href="../concepts/Body.html" title="Body"><span class="bold"><strong>Body</strong></span></a><span class="special">,</span>
    <span class="keyword">class</span> <a class="link" href="../concepts/Fields.html" title="Fields"><span class="bold"><strong>Fields</strong></span></a><span class="special">,</span>
    <span class="keyword">class</span> <a href="../../../../../../doc/html/boost_asio/reference/WriteHandler.html" target="_top"><span class="bold"><strong>WriteHandler</strong></span></a><span class="special">&gt;</span>
<a href="../../../../../../doc/html/boost_asio/reference/asynchronous_operations/automatic_deduction_of_initiating_function_return_type.html" target="_top"><span class="emphasis"><em>DEDUCED</em></span></a>
<span class="identifier">async_write_header</span><span class="special">(</span>
    <span class="identifier">AsyncWriteStream</span><span class="special">&amp;</span> <span class="identifier">stream</span><span class="special">,</span>
    <span class="identifier">serializer</span><span class="special">&lt;</span> <span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">Fields</span> <span class="special">&gt;&amp;</span> <span class="identifier">sr</span><span class="special">,</span>
    <span class="identifier">WriteHandler</span><span class="special">&amp;&amp;</span> <span class="identifier">handler</span><span class="special">);</span>
</pre>
<h5>
<a name="beast.ref.boost__beast__http__async_write_header.h1"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__http__async_write_header.description"></a></span><a class="link" href="boost__beast__http__async_write_header.html#beast.ref.boost__beast__http__async_write_header.description">Description</a>
      </h5>
<p>
        This function is used to write a header to a stream asynchronously using
        a caller-provided HTTP/1 serializer. The function call always returns immediately.
        The asynchronous operation will continue until one of the following conditions
        is true:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            The function <a class="link" href="boost__beast__http__serializer/is_header_done.html" title="http::serializer::is_header_done"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">is_header_done</span></code></a> returns <code class="computeroutput"><span class="keyword">true</span></code>
          </li>
<li class="listitem">
            An error occurs.
          </li>
</ul></div>
<p>
        This operation is implemented in terms of zero or more calls to the stream's
        <code class="computeroutput"><span class="identifier">async_write_some</span></code> function,
        and is known as a <span class="emphasis"><em>composed operation</em></span>. The program must
        ensure that the stream performs no other writes until this operation completes.
      </p>
<h5>
<a name="beast.ref.boost__beast__http__async_write_header.h2"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__http__async_write_header.parameters"></a></span><a class="link" href="boost__beast__http__async_write_header.html#beast.ref.boost__beast__http__async_write_header.parameters">Parameters</a>
      </h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Name
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">stream</span></code>
                </p>
              </td>
<td>
                <p>
                  The stream to which the data is to be written. The type must support
                  the AsyncWriteStream concept.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">sr</span></code>
                </p>
              </td>
<td>
                <p>
                  The serializer to use. The object must remain valid at least until
                  the handler is called; ownership is not transferred.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">handler</span></code>
                </p>
              </td>
<td>
                <p>
                  Invoked when the operation completes. The handler may be moved
                  or copied as needed. The equivalent function signature of the handler
                  must be:
                </p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"> <span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span>
    <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">error</span><span class="special">,</span>        <span class="comment">// result of operation</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span>   <span class="comment">// the number of bytes written to the stream</span>
<span class="special">);</span>
</pre>
                <p>
                  Regardless of whether the asynchronous operation completes immediately
                  or not, the handler will not be invoked from within this function.
                  Invocation of the handler will be performed in a manner equivalent
                  to using <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_context</span><span class="special">::</span><span class="identifier">post</span></code>.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<h5>
<a name="beast.ref.boost__beast__http__async_write_header.h3"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__http__async_write_header.remarks"></a></span><a class="link" href="boost__beast__http__async_write_header.html#beast.ref.boost__beast__http__async_write_header.remarks">Remarks</a>
      </h5>
<p>
        The implementation will call <a class="link" href="boost__beast__http__serializer/split.html" title="http::serializer::split"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">serializer</span><span class="special">::</span><span class="identifier">split</span></code></a> with the value <code class="computeroutput"><span class="keyword">true</span></code> on the serializer passed in.
      </p>
<h5>
<a name="beast.ref.boost__beast__http__async_write_header.h4"></a>
        <span class="phrase"><a name="beast.ref.boost__beast__http__async_write_header.see_also"></a></span><a class="link" href="boost__beast__http__async_write_header.html#beast.ref.boost__beast__http__async_write_header.see_also">See Also</a>
      </h5>
<p>
        <a class="link" href="boost__beast__http__serializer.html" title="http::serializer"><code class="computeroutput"><span class="identifier">http</span><span class="special">::</span><span class="identifier">serializer</span></code></a>
      </p>
<p>
        Convenience header <code class="literal">&lt;<a href="../../../../../../boost/beast/http.hpp" target="_top">boost/beast/http.hpp</a>&gt;</code>
      </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2016, 2017 Vinnie Falco<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
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